Oxidation process



h -cl f? United States Patent- OXIDATIGN PROCESS Gordon HowardWhitfield, Norton-on-Tees, England, assignor to Imperial ChemicalIndustries Limited, London, England, a corporation of Great Britain NoDrawing. Filed Jan. 20, 1958, Ser. No. 709,751

Claims priority, application Great Britain Feb. 8, 1957 8 Claims. (Cl.260-524) This invention relates to a process of liquid phase oxidation.

Prior to the present invention there was a large number of processes forthe oxidation of organic compounds in the liquid phase by means ofoxygen or ozone containing gases. Included among these were a processfor the oxidation of aliphatic aldehydes to the corresponding carboxylicacids using catalysts of variable valence such as man ganese, cobalt, orlead, acetates; and a process for the oxidation of alkyl aromatichydrocarbons to the corresponding carboxylic acid using as catalyst ametal or mixture of metals of variable valence, if desired together withhalogen or a halide, e.g. bromine, which was some times conducted in thepresence of a solvent, e.g. a lower aliphatic monocarboxylic acid.

We have found that in processes of these sorts the aliphatic carboxylicacid is degraded and that the efliciency of the process falls because oflower yield, and/or the operating costs rise because of degradation ofthe relative:

1y expensive aliphatic acid and of the need for removing the degradationproducts. We have now found that in 7 these processes the aforesaiddisadvantages may 'be considerably decreased by arranging for thepresence --in the reaction medium of basic ions.

According to this invention there is provided a process for theoxidation of organic compounds conducted in the liquid phase by means ofmolecular oxygen or ozone employing as catalyst at least one metal ofvariable valence, in which a saturated aliphatic monocarboxylic acid ispresent as medium, or product of reaction, characterised in that theoxidation is conducted in the presence of cations corresponding to aconcentration within the. range.

of from 0.25 to 0.00025 gram atom per gram mole of total organiccompounds, preferably from 0.05 to 0.0025

gram atom per gram mole aforesaid. If several organic compounds arepresent, then the gram mole specified in the above definition is takenas the sum of the gram mole fractions of the said compounds. While it isdesirable, it

is not necessary, that all of the cation is in ionic'form.

While the use of any basic ions is within the scope of .the invention itis preferred to use those of the alkali metals or alkaline earth metals:lithium, sodium, potassium, rubidium, caesium, calcium, strontium andbarium. Beryllium, magnesium, zinc and cadmium are also effective but toa lesser degree. Suitable compounds of the metals are, for example, theoxides, hydroxides, carbonates, phosphates, halides, or carboxylates,e.g. acetates, propionates, naphthenates. Basic ions seem to modify thecatalyst. i

In the oxidation of aliphatic aldehydes to acids according to theprocess, suitable catalysts comprise, for example, compounds ofmanganese, cobalt, lead or cerium.

- to r the metal of variable valence.

icatalyst's are the mixed bromides of manganese and cobalt.

This process is of especial value for the production of saturatedaliphatic acids from the corresponding aldehydes, especially thosecontaining in the molecule from 2 to 15 carbon atoms. The followingprocedure is especially suitable for the oxidation of propionaldehyde,but is also applicable to the oxidation of the other aldehydes. Withhigher aldehydes it may be desirable to use a solvent, e.g. an aliphaticacid.

The metal of variable valence is preferably either manganese or cobaltor combinations thereof, added in a total metal concentration of between1.0 and 0.00001 gram atom per gram mole of propionaldehyde, more usuallywithin the range 0.001 to 0.00001 gram atom/ gram mole of aldehyde.Basic ions of the types defined above are added at a concentration offrom 0.25 to 0.00025 gram.

atom per gram mole of organic compound present, usual: ly from 0.05 to0.0025 gram atom per gram mole, added e.g. as carboxylate such aspropionate, acetate; or as mono-, dior tri-basic phosphates; or ashalides etc. Oxidation temperatures may be between 0 and 150 C., and itis an advantage of the process that higher oxidation temperature may beused in the presence of basic ion, as this latter prevents degradativeoxidation of the product. A higher oxidation temperature enables thereaction to be controlled by water cooling and hence avoidsrefrigeration, whichis expensive. The oxidising gas may be air or oxygenat atmospheric pressure, elevated pressure, or even subatmosphericpressure. Means for dispersing the gas in the liquid may be provided oralternatively for dispersing the liquid in the gas. Such processes maybe operated batchwise or continuously.

The oxidation of alkylated compounds of aromatic in the presence of analiphatic monocarboxylic acid and of a metal of variable valence can beconducted at, for example, 50 to 300 C. and at atmospheric or super-.atmospheric pressures of up to 200 atmospheres. The catalysts may beemployed as compounds of the metals such as their carboxylates, e.g. theacetates, propionates, nonanoates, naphthenates, of manganese, cobalt,lead cerium, vanadium etc. Improved results are obtained in this processwhen the catalyst comprises halogen or a halide, especially bromine, inaddition Especially suitable It is'often convenient to introduce thebasic ion in chemical combination with bromine, e.g. as sodium,potassium, calcium or barium bromide. Suitable proportions of thecatalytic substances are from 1 to 0.0005 gram atom of total metal pergram mole of oxidisable starting material,

preferably 0.1 to 0.001 gram atom of total metal per gram moleaforesaid; and of halogen, e.g. bromine,'from' 2 to '0.001 gram atomsper gram mole of starting material, preferably from 0.2 to 0.002 gramatom per gram mole aforesaid. The ratio of the one metal to the othermay be varied within these ranges of total metal. Preferably the ratioof manganese to cobalt is about 2:1, although up to about 9:1 gives goodresults. Suitable proportions of manganese dibromide (MnBr AH O) and ofcobaltous bromide (CoBr .6H O) are, respectively, 0.1 to 200%,preferably 0.65 to 0.85%, and 0.05 to 100%, preferably I 0.33 to 0.48%by'weight of the compound to be oxidised,

If desired halogens, especially bromine may also be present, e.g. as thehalides of metals of variable valence. 1f halogen is present the basicion may be introduced as a compound of the halogen, e.g. sodium bromideor barium bromide. In this process fairly wide ranges of temperature maybe used, e.g. 0 to 150 C. Pressure is not necessary, but may be used ifdesired. 1- if;

assuming a molecular weight of and proportionally for other compounds.

Examples of alkyl aromatic hydrocarbons which can be oxidised to thecorresponding acids according to the process are: the xylenes whichyield the corresponding phthalic acids; the diisopropyl benzenes whichalso yield the corresponding phthalic acids; toluene or cumene which.yield benzoic' acid; mesitylene which yields trimesic acid;methylnaphthalenes which yield naphthoic acids; and

esters such as benzylbenzoate which yields benzoic 'acid,

Patented Nov. 8, 1960 and methyl para-toluate, which yields methylhydrogen terephthalate. However, it has been found difiicult to oxidisetertiary carbon atoms directly attached to a carbon of the ring.Examples of oxygenated derivatives 4 EXAMPLE 2 This experiment wasconducted in the manner of Example 1 with a charge consisting ofpropionic acid (200 grams), CBr 6I-1 O (1.0 gram), Co(OAc) 4H O (5.0

which can be oxidised to the corresponding acids accord- 5 grams) andMnBr 4H O (0.1 gram). Well dispersed mg to process beniyl i WhlFh f henoxygen was passed at a rate of 12 litres/hour through the 201C and;benzald-ehyde winch yields benzolc acldiacet? boiling solution and waterwas continually removed as E- i Ta i g ifi acld; and paratolmc andformed. Throughout a four hour oxidation period the yle 5 rep c c1 exitgas stream contained an average of 29.7 volume Examples of hetel-AoFychccompounds of w Ch?- percent of carbon dioxide and at the end of thisperiod 23?; gi ggfi gggg g gijg afi 2 522 pyndmes which carbon dioxidewas still being vigorously evolved. At Moreover, hydrocarbons ofaromatic character subthls 9 gram of q bromlde 5 added and 1 evolutionof carbon dioxide and format1on of water stituted by at least one alkyl,haloalkyl or closely related ceased Showin Su mssion of oxidativedegradation of oxygenated derivative of an alkyl or haloalkyl group and15 the pnjpionic agcid the hour followino the f$g 2 6 ffsii i ii gjigfiii gf 2 :33 dition of the sodium bromide .the average carbon dioxide i(Rjalkyl, a W21) NHCOR 3 or content of the exit gas stream was 0.5volume percent. -O'COR (R=alkyl, aryl or H), SO R (R=alkyl, aryl or H),-CONRR" (R=alkyl, aryl or H), NRR" EXAMPLE 3 (R=alkyl, aryl), benzoyl,substituted benzoyl or alkyl Blank carboxylic ester, can also beoxidised to the corresponding carboxylic acids. Examples of suchcompounds are: A charge consisting of 600 grams of propionic acid,paraand meta-chlorotoluene;paraand meta-toluene sul- 0.59 gram of cobaltbromide (CoBr .6H O) and 1.14 phonamides; paraand meta-cresyl benzoates;para- 26 grams of manganese bromide (MnBr .4H O) was heated toluenesulphonic acid; methyl para-toluene suphonate; to 180 C. in a stainlesssteel reactor under an oxygen para-toluamide; beta-picolincs. Thehalo-methylation pressure of 150 p.s.i.g., and oxygen at a pressure of150 products of toluene or benzene, especially the chlorop.s.i.g. wasintroduced at a rate of 200 litres/hour (measand bromoones, may also beoxidised according tothe ured at atmospheric pressure into the bottom ofthe reinvention to the corresponding carboxylic acids. 30 actor througha /s" bore standpipe for 8 hours. Samples The molecular oxygen may beintroduced as air or of the exit gas were analysed periodically foroxides of diluted air or as ozonated air. carbon and the figuresobtained were as follows:

Time: hours 0.25 1.25 2.25 3.25 4.25 5.25 0.25 7.25

Volumwmentmofl-Wf- {88' 2:3 3:3 1:? ii? 28 i3 :13: i3

EXAMPLE 5 1 In a blank experiment oxygen in well dispersed form waspassed at the rate of 12 litres per hour through 200 grams of propionicacid containing 1.0 gram of COBI'26H2O (ii) Operation according to theinvention The above experiment was repeated in identical manner exceptthat 6.0 grams of sodium hydroxide was 6 added. The following resultswere obtained.

Volume percent in ofl-gas of.

at the boiling point of the liquid (137 C.) underatmospheric pressurefor 7 hours. Analysis of the'exit gas stream showed 28.6 volume percentof carbon dioxide and 12 grams of water, which is clear evidence ofconsiderable degradative oxidation of the propionic acid.

Operating according to the invention, 200 grams of propionic acidcontaining 1.0 gram of CoBr 6H O and 5.0 grams of sodium bromide wastreated in exactly EXAMPLE 4 The experiments described in Example 3 wererepeated using acetic acid (600 grams) in place of propionic acid.

0 The results, given below, show that in this case also oxidativedegradation is suppressed by addition of the sodium similar manner as inthe blank experiment. Analysis of 011- Time: hours 0.25 1.25 2.25 3.254.25 5.25 6.25 7.25 Experiment 00, 1.4 0.0 0.7 1.0 0.8 0 5 0.7 0.8}With0ut sodium V 1 in ft f 00 1.2 1.0 0 0 0 0 0 0 wliyhdrolxlidg.mepemem -co, 0s 0s '02 02 02 05 0s 02{ sodium by Co 1.0 0 0 0 0 0 0 0 mmEXAMPLE 5 ''the' exit gas stream showed the absence of carbon dioxideand of water.

This is clear evidence of the inhibition of degradative oxidation of thepropionic acid.

The experiments described in Example 3 were repeated except that bariumhydroxide, .Ba(OH) .8H O (4,7,.3

grams) was added in place of sodium hydroxide. The results given belowindicate that barium is eifective also in suppressing oxidativedegradation. The blank experiment was carried out immediately before therun using barium, in order to be certain that conditions were such thatdegradation would still occur, i.e., that no sodium remained in thereactor.

(NaOAc.3H O). In this case also oxygen uptake was almost complete andthe reaction over in 5 hours. The product weighed 252.7 grams, and 1.3grams of material was collected in the cold catch-pots.

In contrast, however, the carbon dioxide content of the exit gas in thisrun was extremely small, and analysis of the reaction product as in (i)showed the following yields Time: hours 0.25 1.25 2.25 3.25 4.25 5.256.25 7.25 Experiment wit out ar um. Vmumepelcentmmgawt CO: 0 1.0 0.5 0.50.5 1.0 1.0 }With barium hy- 00 0 0 0 0 0 0 0 0 droxlde added.

EXAMPLE 6 based on propionaldehyde remaining in the reactor:'

This illustrates the use of sodium ion to suppress degradation in theautoxidation of propionaldehyde to propionic acid.

(i) Blank The charge consisting of 200 grams of propionaldehyde/waterazeotrope (98% propionaldehyde) and 0.1 gram of manganese acetate(Mn(AOc) .4I-I O), was held in a glass reactor and 12 litres/hour ofoxygen was introduced at atmospheric pressure through the hollow shaftof a cruciform stirrer revolving in the reaction mixture at 1000 r.p.m.The ofi-gas line from the reactor contained two water condensers and twocold catch-pots. The temperature in the reactor was held at 25 to 30 C.by means of an external cooling bath containing circulating water. Theoff-gas from the reactor was mixed with air fed at 12 litres/ hour andfrequent Orsat analyses of the mixtures were carried out for oxygen andcarbon oxides. Oxygen uptake was rapid and almost complete, and ceasedafter 5 hours. Thereafter the oxidation was stopped.

During most of the oxidation the off-gas contained 8 to 10% by volume ofcarbon dioxide. Separation and estimation of acids in the reactionproduct (228.0 grams), by means of liquid phase partitionchromatography, estimation of aldehyde polargraphically, and estimationof propyl propionate by ester value, indicated the following yieldsbased on propionaldehyde remaining in the reactor, due allowance beingmade for material entrained and collected in the catch-pots (7.6 grams).

Percentage conversion of propionaldehyde 7 a by weight to: Y

Formic acid 0 Acetic acid 0 Propionic acid 91.7 Propyl propionate 3.6Unchanged 0.9

Totally to carbon oxides and unaccounted for 3.8

Clearly, the addition of sodium acetate actively suppresses oxidativedegradation to lower acids and oxides of carbon and causes a substantialincrease in the yield of propionic acid.

EXAMPLE 7 It has been shown above that the presence of basic ion greatlydecreases the oxidative degradation of propionic acid. The data givenbelow show that the presence of alkali metal ion does not adverselyaifect the oxidation of an alkyl aromatic compound in propionic acid assolvent.

The oxidation of para-xylene (40 grams) dissolved in propionic acid (200grams) was performed in the presence of the catalysts specified in thetable below at the boiling point (about 137 C.) using an oxygen rate of12 litres per hour. The concentrations of manganese and cobalt in runs 1and 2 are the same as in runs 3 and 4.

Catalyst Purity of Molar Weight of terephconversion Run No. Time,terephthalic acid to tereph- Manganese Cobalt Additive, hours thalicacid, by acid thalic compound, compound, grams grams value, acid,

grams grams percent percent Mn(Ac)z 00(Ac); NaBr 0.2 0.1 5.0 7 47.0 96.672.6 0.2 0.1 5.0 20 57.9 97.4 90.1 MllBlg4HgO COB12.6H20

Percentage conversion of propionaldehyde Thus run 2, in which 0.016 gramatom of sodium was by weight to: present per gram mole of total organiccompound, gave Formic acid 0.7 quite as good molar conversion ofpara-xylene to tereph- Acetic acid 6.4 thalic acid in 20 hours andtherefore quite as high a Propionic acid 81.3 reaction velocity as run 4in which no sodium was present, Propyl propionate 5.1 and this underconditions Which cause very little oxida- Unchanged 1.0 tive degradationof propionic acid. Totally to carbon oxides and unaccounted I claim:

for 5.5 1. In processes for the production of carboxylic acids byoxidation in the liquid phase of at least one member 100.0 selected fromthe group consisting of aliphatic aldehydes,

(ii) Operation according to the invention A run was carried out exactlyas above, except that the charge contained 5.0 grams of sodium acetatealkyl aromatic hydrocarbons, alkyl aromatic heterocyclic compounds,having alkyl groups as the sole substituents, and closely relatedoxygenated derivatives of these classes of compounds; with oxygen gas inthe presence of a bromine compound and as catalyst a metal selected fromthe group consisting of cobalt and manganese, and in the presence of asaturated aliphatic monocarboxylic acid, the improvement which consistsin inhibiting the oxidative degradation of said aliphatic monocarboxylicacid by conducting said process in the further presence of a cationselected from the group consisting of alkali and alkaline earth metalcompounds in an amount corresponding to a concentration within the rangeof from 0.25 to 0.00025 gram atom per gram mole of total organiccompounds.

2. A process as claimed in claim 1, in which the starting material ispropionaldehyde and propionic acid is produced.

3. A process as claimed in claim 1, in which said concentration of saidcation corresponds to from 0.05 to 0.0025 gram atom.

4. A process as claimed in claim 1, wherein said starting material isxylenes.

5. A process as claimed in claim 1, wherein said starting material isdi-isopropyl benzene.

6. A process as claimed in claim 1, wherein said starting material istoluene.

.7. A process as claimed in claim 1, wherein said starting material iscumene.

8. A process as claimed in claim 1, wherein said starting material ispara-toluic acid.

References Cited in the file of this patent UNITED STATES PATENTS2,223,494 Loder Dec. 3, 1940 2,245,528 Loder June 10, 1941 2,287,537Schulz June 23, 1942 2,444,924 Farkas et al July 13, 1948 2,833,778Safler et al May 6, 1958 2,833,816 Safier et al May 6, 1958

1. IN PROCESSES FOR THE PRODUCTION OF CARBOXYLIC ACIDS BY OXIDATION INTHE LIQUID PHASE OF AT LEAST ONE MEMBER SELECTED FROM THE GROUPCONSISTING OF ALIPHATIC ALDEHYDES, ALKYL AROMATIC HYDROCARBONS, ALKYLAROMATIC HETEROCYCLIC COMPOUNDS, HAVING ALKYL GROUPS AS THE SOLESUBSTITUENTS, AND CLOSELY RELATED OXYGENATED DERIVATIVES OF THESECLASSES OF COMPOUNDS, WITH OXYGEN GAS IN THE PRESENCE OF A BROMINECOMPOUND AND AS CATALYST A METAL SELECTED FROM THE GROUP CONSISTING OFCOBALT AND MANGANESE, AND IN THE PRESENCE OF A SATURATED ALIPHATICMONOCARBOXYLIC ACID, THE IMPROVEMENT WHICH CONSISTS IN INHIBITING THEOXIDATIVE DEGRADATION OF SAID ALIPHATIC MONOCARBOXYLIC ACID BYCONDUCTING SAID PROCESS IN THE FURTHER PRESENCE OF A CATION SELECTEDFROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METAL COMPOUNDSIN AN AMOUNT CORRESPONDING TO A CONCENTRATION WITHIN THE RANGE OF FROM0.25 TO 0.00025 GRAM ATOM PER GRAM MOLE OF TOTAL ORGANIC COMPOUNDS.